"We found that 36 per cent of women are having sex or sexual contact in prison, which really is quite a lot of sex," News.com.au quoted lead researcher Juliet Richters, a public health specialist at the University of NSW, as saying.
The researchers attribute the high sexual activity among women to the fact that there are fewer taboos.
Discussing another reason for it, the researchers said that almost a third of female prisoners identified themselves as lesbian or bisexual.
"We don't know why that is but it might be that women with children are more likely to be given a non-jail form of punishment," Juliet said.
"But the picture among men is very different," she added.
The survey was also carried out on more than 1000 NSW men, and it was revealed that just six per cent of the men had sexual contact in jail, with five per cent of it deemed consensual.
Most of the men revealed that they did it for pleasure, with less than one per cent trading sex for food or tobacco, and about 30 per cent of men admitted to having feared sexual assault behind bars, which in reality is very rare.
"We found most men strongly disapproved of sex in prison and considered those who did it to be gay," she said.
"There's not a lot of sex because they're so concerned to protect their reputation as a heterosexual that they're really careful to avoid anything like that.
"We've shown that the whole belief that young and attractive people are likely to be raped in jail is a bit of a myth.
"It's pretty safe these days, especially with the modern prisons with things like showers in cells," Dr Richters added.
The study, released at a sexual health conference in Perth, also gave a rare glimpse of other aspects of prisoners' health and welfare.
It showed that about 80 per cent smoke and more than half had injected drugs in their lifetime.
Half the men believed that abortion was always wrong, and 23 per cent thought sex between women was unnatural.
A third of men and 27 per cent of women said that they had been physically assaulted while in jail, a figure Juliet said was "probably a similar reflection of their life before jail".